In function development of control unit software, in particular in automotive control units for controlling the engine, brakes, transmission, etc., the bypass application is a rapid prototyping method for developing and testing new control unit functions. However, such development of functions is also possible with all other control unit applications, e.g., in the field of automation and machine tools.
Two applications of external control unit bypass, as described in German Patent Application No. DE 101 06 504 A1, for example, and of internal control unit bypass, as described in German Patent Application No. DE 102 286 10 A1, for example, may be used as development methods here.
German Patent Application No. DE 101 06 504 A1 describes a method and an emulation device for emulating control functions and/or regulating functions of a control unit or regulating unit of a motor vehicle in particular. For emulation, the functions are transferred to an external emulation computer, a data link being established via a software interface of the emulation computer and a software interface of the control unit/regulating unit before the start of emulation. To greatly accelerate the development and programming of new control/regulating functions of the control unit/regulating unit, the software interfaces configured for emulation of different control/regulating functions before the start of emulation without any change in software.
German Patent Application No. DE 102 286 10 A1 describes a method and a device for testing a control program by using at least one bypass function in which the control program is executed together with the at least one bypass function on an electric computing unit. The bypass functions are coupled to preselected interfaces via dynamic links.
Independently of these two methods and devices, interventions in the control unit software are necessary for applicability. Such interventions are referred to with the term bypass breakpoint or software breakpoint. A bypass breakpoint, i.e., software breakpoint, describes exactly the location in a software function where the content of a control unit variable is not described by the software program but instead is described via detours, e.g., via a bypass software function. Software breakpoints are highly individual and in the normal case are not part of a control unit software program because memory resources are used for this.
If a function developer requires a control unit program having software breakpoints, these are incorporated into a program version only after the development department has been commissioned. For this purpose, the software development manually modifies the source code of the corresponding function and, by running a compiler and link, creates a new control unit program which is used explicitly for the prototyping application.
A disadvantage of the conventional method and device includes the long running time until availability of the rapid prototyping program version. An important factor here is the high technical and administrative cost for the specification and implementation of the software interventions.
According to the information currently available, a comparable method is based on the idea of replacing only the store instructions (write access to a control unit variable) via jump instructions to a subfunction. However, in microcontrollers having a mixed instruction set (16/32-bit CPU instructions), the store instructions may already be 16 bits because addressing is performed indirectly via address registers. These 16-bit instructions cannot be used to call a subfunction because a direct address-oriented call of a subfunction requires a 32-bit jump instruction. Therefore, the conventional method is usable only to a limited extent and may be used only with microprocessors having a pure 32-bit instruction set. In other words, when the store instruction has a fixed bit width, flexibility with regard to the function development is greatly restricted here. This is also true when a certain store instruction must not be manipulated at all for other reasons, so that populating in this way via a jump instruction to a subfunction is then not possible at all.